


_Ji^ ^ "* "V'v 


> _7» .» 


> > 




~~y> v> » 


> ^ ^ 


> 


-> ;>:> 


^t> 2> » 


- >-?"•* i3P 


- X 


■> > > 


>^> ^>:> >:> 


- - > »"3» > 


) 


;>~> 


xj» "5^ >^ 


> > > r^ J3fc 


> 


>> 


»~3§^ ■*«■ ->> 


: ^T» ^3» 


> 


, > ;> 


TSEM^ T ~> ~3> 


^ >A^3 


► ) 


- >:> 



:>» vi c* » ~>_23P> - ■■-•:>. > > 

> ) )> > > » c> ->■> "> '*> -= 

>>> y^ ■ > • . V-"j> > *•> > > > -= 

> :>»»>/ 3 - J> > > ^> >„ 



> > » . > J> 












» 






>^» > :>> ^>.^ ; < 



^>^ >i>'» > 



- s-> 












> 



I LIBRARY OF CONGRESS. I 



>>„~s> ■> .■>:> 
->> >> j ^ *^ 

y »-> - 
> t> ' ^ 

5 > 



W/Aafi. 



^Yie/f 4 U6. " 



> > > J^ 
> > > >^ 









J UNITED STATES OP AMERICA, f 






> > > > s> 

>^» > > '^= < 

;»> > * >^> > 

^ "^ ~>> O 









r>>-5> O 

V .> ■> i 






> > >> 



t> yi?5. 












— > > ^ - 
>5 3> ^ 4? ^> 









y^ 



> d :> 



-> ^v 5 * , 



^^> 



.,s ~> 






^^ 



"V> ^J*- 



■■■> > : 
> > 



^> ) > :> > 



^®? 



^ 



?>f, 








>. ^c_ 3^ 


r . ■ ? » > . • 
, > > > . ^> 


o>££^ 


** a£ 






^»^?>9 












^ > ^ >> >> -> 1 












> > 

> > 



■> > '■■■-'- 



- *-> > - 






>^ 3 ? 





















>> SJ> |N ' -» -^ -? 



>> ^> 

3 >. > ■■- 



i > • sat, ^ 



>■ > ^ 


















> ~^ - - 
>^> > 












^ :>v> 

>:> 



> .;xe> 



7*^ 















»> ^ 












^> 



sv> > >> 



United States Hydrographic Office.— Bureau of Navigation. 



HURRICANES; 



WITH 



NAUTICAL DIRECTIONS FOR AVOIDING 



AND 



MANEUVERING IN THEM. 



WASHINGTON: 

GOVERNMENT PRINTING OFFICE 

1872. 



United States Hydrographic Office.— Bureau of Navigation. 



HURRICANES; 



WITH 



NAUTICAL DIRECTIONS FOR AVOIDING 



AND 



3?fc 



£fWA 



MANEUVERING IN THEM. 



■^■j ♦ *-^- 



WASHINGTON: 
OOYERNMENT PRINTING OFFICE 

1872. 



(fV 



The following extracts are from the valuable works of the late G. 

Phillipe de Kerhallet, captain, French navy, &c, and from the Memoirs 

on Hurricanes, &c, by Mons. M. Keller, hydrographic engineer, French 

navv : 

R. H. W. 

United States Hydrographic Office, 

April 2, 1872. 



Hurricanes* take place in the three great seas of the Hurricanes. 
globe : the Atlantic, the Indian, and the Pacific Oceans. 

In the Atlantic Ocean, the West Indies is the center of 
the most terrible hurricanes known. In the Indian Ocean 
it is about the position of Rodriguez, Mauritius, and Re- 
union Islands. In the Pacific, where very few observations 
have thus far been made, it is supposed to be in the vicinity 
of the Tonga Islands. 

In the West Indies and their vicinity, the season during Period of hum- 

J ' & canes. 

which hurricanes may be expected includes the months of 
August, September, and October ; f at this period the navi- 
igation of the West Indies, of the Gulf of Mexico, and 
south coast of the United States should be avoided as 
much as poss 

If it is necessary to winter in these localities, a perfectly 
protected port should be chosen. Hurricanes seldom occur 
in June or July. 

In the Indian Ocean, hurricanes take place from Decem- 
ber to April ; that is, during the warmest months of the 
southern hemisphere $ they seldom occur in November and in 
May, and are unknown during the other months of the year. 

* For a more complete description of hurricanes, &c, we would refer 
mariners to the excellent treatise of M. Keller, hydrographic engineer, 
Paris. Traite sur les Ouragans, <$c, and also to Silliman's Journal ; to 
Reid, Attempt to Develop the Laivs of Storms ; to Thorn, Inquiry into the 
Nature and Laws of Storms ; to Piddington, Horn-Boole of Storms, Observa- 
tions on Revolving Storms, British Admiralty ; and the Memoir on the Storms 
of the East Indies, hy Lieutenant Lefehvre. 

t According to Blodget : Climate of the United States, (p. 400,) from 
ohservations extending over nearly four centuries, hurricanes have 
occurred in the West India Islands and their vicinity in the following 
ratio per 100 for the different months of the year : 

January, 1.5; Fehruary, 2; March, 3; April, 2: May, 1.5; June, 3 ; 
July, 7 ; August, 28.5 ; Septem her, 24 ; October, 20.5 ; November, 5 ; De- 
cember 2. 






In the Pacific Ocean, to the south of the Equator, the 
known liurricaDes have taken place in November and in 
December, and they appeal to have much similarity to 
those of the Indian seas. 
^pogd j n t | ie Atlantic Ocean, to the north of the Equator, the 
f^^^^^i supposed extent of the zone where kuirieanes are experi- 

ricanes arc nitL - 1 - *- *- 

enced is comprised between the latitude of 10 c and 50~ y. 
and the longitude of o0- and 100- W. 

In the Indian Ocean, the extent of this zone in longitude 
is three thousand miles, from the west coast of Australia to 
that of Madagascar, and is comprised between the latitude 
of 6~ or 8° S. and 22" S. 

Having indicated the different treatises published on hur- 
ricanes, we cite particularly that of 31. Keller and the me- 
moir of M. Lefebvre. and would refer all seamen who may 
wish to familiarize themselves with the manner in which 
the general laws of storms are deduced from theory, as 
also the practical rules for escaping their violence, to these 
works. This subject does not enter into the plan of this 
memoir, in which, we only state facts without searching for 
the causes. We will limit ourselves to giving the general 
laws of hurricanes, as deduced from numerous observations, 
together with practical directions. 

These tempests have a double movement : the one gyra- 
tory, or rotary, the other of translation, or movement from 
one place to another.* 
move- To the north of the Equator the gyratory movement is 
from the right to the left in passing by the X. : that is to 
say. in an opposite direction to the movement of the hands 
of a watch. In the southern hemisphere on the contrary, 
it is from left to right in passing by the y.. or in the same 
direction as the movement of the hands of a watch. 
Movement of The movement of translation is upon a parabolic curve, 
the apex of which is always turned toward the W., and the 
branches throw themselves out to the E. The apex, of thi> 
curve is tangent to the meridian about the latitude of 30 : 
in the northern hemisphere and about that of 26° in the 
southern hemiphere : that is to say. nearly at the polar 
limits of the trade- winds. The hurricane moves on this 
curve in departing from the Equator: in other words, the 
point of departure of the hurricane is at the eastern ex- 
tremity of the curve of its path nearest approaching the 
Equator, and in a latitude nearly equal to the declination 
of the sun : from thence, the hurricane, in the first half of 



* The following is taken from the treatise oi M. Keller. 



its course, is directed toward the apex of the curve, or to- 
ward the W. ; then it follows this apex as tangent to the 
meridian, bending afterward to the E., in the portion of the 
curve of its path the farthest removed from the Equator. 

The velocity of the translation is in proportion to the vio- veioci ty of 

^ it translation. 

lence of the tempest. In the mildest hurrncanes observed 
it has not been less than ten miles an hour, and in the most 
violent it has not exceeded thirty miles.* 

Nearly all authors on this subject, observes M. Lefebvre, Diameter of the 
have sought to measure the diameter of the vortex, and, v< 
this diameter being known, to determine from the force of 
the wind and the falling of the barometer at what distance 
the observer was from the center. They have succeeded 
but indifferently ; the diameter of the vortex of hurricanes 
is very variable. M. Keller states that the initial diameter 
of the gyratory movement is from 3° to 4° of the terrestrial 
arc, and that it increases progressively as it advances, until 
it attains 8° or 9° at the extremity of the curve of its path. 

In the northern hemisphere, the vessels placed on the Dangerous 
edge of the right parallel to the path of the center, and in 
the southern hemisphere those placed on the edge of the 
left, are those most injured. 

A ship surprised by a hurricane perceives successively 
every direction of the rotary movement of the air on a 
secant parallel to the path of the center of the meteor jt 
these changes of direction never make the tour of the com- 
pass. When the secant traverses the center of the meteor 
the wind changes sixteen points at the center perpendicu- 
larly to the line of translation, and after an interval of 
calm. 

Od each secant the barometer falls gradually to the in- oscillations of 

the barometer. 

stant of the passage of the point nearest the center, then 
it rises progressively from this moment until the end of the 
tempest, which corresponds to the extremity of the secant. 
But, says M. Lefebvre, the violence of the wind is no more 
connected with the diameter of the vortex than the fall of 
the barometer is. The wind increases as the center is ap- 
proached, and the barometer constantly falls; this is all 

* M. Lefebvre states that for the Indian Ocean these velocities are too 
great, and he estimates for the movement of translation a velocity of 
from five to six miles an hour, as a mean, for, he adds, hurricanes do not 
change their place hut at a rate of velocity of two miles per hour. — 
Memoir on the Hurricanes of the Indies, <$-c, page 12. 

t Some authors state that in these tempests the wind attains a ve- 
locity of even ninety miles an hour. 



6 

that can be said. To attempt to establish a general rule on 
this point would most likely lead to error.* 

Such, according to M. Keller, are the laws principally ob- 
served in hurricanes. These laws known, the attempt has 
been made to utilize them, and to give to seamen the means 
of avoiding the violence of these terrible phenomena. The 
two problems to solve were these : 1st, to determine in a 
hurricane the position occupied by the vessel in relation to 
the movement of translation of the meteor j 2d, this posi- 
tion known, to determine which may be the best maneuver 
to make to receive the hurricane or to cross it in the man- 
ageable semicircle. The first problem is easily resolved, 
and M. Keller has given us on this subject a very important 
general rule which can be applied to every type of tempest, 
whether they have a convergent or divergent character ; 
that is to say, whether the wind in turning describes a 
circle, or whether it is directed from the circumference to 
the center of the vortex or from its center toward the cir- 
cumference. 

The following is the principle on which can be determined 
in every case whether you are to the right or to the left of 
the path of the storm : f 

" Every vortex, in moving, causes to be felt at fixed points 
on its passage to the left of the path of its center a succes- 
sive change of wind, turning by compass to the left, or in 
an opposite direction to the movement of the hands of a 
watch. It causes to be experienced at points situated to the 
right of this path a succession of winds which turn by the 
compass to the right, with the movement of the hands of a 
watch." 

Thus, when a hurricane threatens, by remaining one or 
two hours in nearly the same position, and observing with 
great care the successive variations of the wind, the posi- 
tion of the vessel with regard to the line of its path can be 
determined without difficulty, and consequently whether 
you are in the dangerous or manageable semicircle. 

In hurricanes of a rotary type it is very easy to determine 
the bearing of the center of the tempest with regard to the 
vessel. We have said, in effect, that in these tempests, 

* Memoir on Hurricanes, <fc\. page 11. 

t Memoir on the Typhoon of 11th to 14th September, 1840, page 3. In a 
memoir much more comprehensive, which includes the researches made 
by M. Keller on hurricanes, which is yet unpublished, the principle 
which we give here in so condensed a shape will be accompanied by ex- 
planations, &c, which will demonstrate its correctness and its practical 
application. 



to the north of the Equator the wind turns from right to 
left, contrary to the movement of the hands of a watch, 
and that to the south of the Equator it turns from left to 
right. Then whatever may be the space occupied by the 
tempest, the wind blows always in describing a circle. Evi- 
dently the center of this circle should be found on the per- 
pendicular to the direction of the existing wind. Conse- 
quently, it is sufficient to determine by compass the direc- 
tion of the wind, and the center will be 90° to the right, if 
in the northern hemisphere, and 90° to the left, if in the 
southern hemisphere. 

In order to avoid error in this particular, the following 
table can be used, which gives at once, from the direction 
of the wind, the bearing of the center of the storm for each 
hemisphere : 



Northern hemisphere. 


Southern hemisphere. 


If the wind is — 


The center bears — 


If the wind is — 


The center bears — 


N 


E 


N 

N. by E 


W. 


X. by E 


E. by S 


W. by N. 
W. N. W. 
N. W. by W. 
N.W. 


N. N. E 

N. E. by ]ST 

N . E 


E. S.E.. 

S. E. by E 


N.N.E 

N. E.byN 


S.E 

S. E.byS 


N.E 


N.E.byE 

E.N. E '.: 


N.E. byE 


N. W. by N. 
N. N. AV 


S.S.E 


e.n.e...: 

E. by N 

E .. .. 


E.byN 


S. by E 


N. by AV 

N 


E 


S 


E.byS 


S. by W 

S.S. w 


E. by S 


N. by E. 

N. N E 


E. S. E 


E. S. E 

S. E. by E 


S.E.by E 


S. W.byS 

s. w 


N. E. by N. 

N E 


S. E 


S.E 


S. E.byS 

S. S.E 

S.byE 


S.W.byW 

W. S. W 

W.byS 

W 


S. E.byS 

S.S.E 

S.byE 


N. E. by E. 
E. N. E. 
E.byN. 
E 


S 


S... . 


S. by W 


W. by N 


S. by W 


E. by S. 

E S E 


s. S.W 


W. N. W 

N. W. by W 

N. W 


S S.W 


S. W.byS 


S. W.byS 

S.W 

S.W.byW 

W.S.W 

W. bvS 


S. E. by E. 

S E 


s. w 


S. W. by W 

W.S.W 


N.W.byN 

N.N.W 


S. E. by S. 

S S E ' 


W.byS 


N. by W 


S. by E. 

S. 

S.byW. 

s. s. w. 

S. W. by S. 

s w 


W 


N 


W 


W. by N 


N. by E 


W bvN 


W.N. W 

N.W.by W 


N. N. E 

N. E. bv N 


W. N. W 

a.w.hjw 

N W 


N.W 


N. E 


N.W.byN 

N. N. W 

N.by W 


N. E. by E 

E.N.E 

E.byN 


N.W.byN 

N.N.W 

N. by W 


S. W. by AV 
W. S. AV. 
AV. by S. 









The bearing of the center of a hurricane from the vessel 
being known, it is certainly desirable to determine its dis- 



8 

tance : for this, however, no precise rule has as yet been 
found. Some very good inferences may be drawn from the 
quickness or sluggishness with which it appears to develop 
itself, from the increasing violence of the squalls, from the 
Irregularity of the sea which rises in several directions, and 
above all from the rapid variations of the barometer. 

A remarkable trait of the rotary gale is the increase of 
the wind in the vicinity of its center, although at the center 
irself it blows so irregularly and by squalls as to render it - 
impossible for a ship to complete a maneuver. The nearer 
the center is approached the more sudden are the changes 
of the winds, which, instead of shifting point by point, as is 
the case at the entrance of the circle of the tempest, it shifts 
all at once sixteen points. The ship is enveloped in a ter- 
rible squall, and gathers stern-board against a frightful sea, 
the disastrous consequences of which it would beuuncessary 
to detail. 

The undulations and currents of hurricanes appear to be 
the constant results of these violent atmospheric shocks. 
These two phenomena deserve to be the subject of serious 
study and research. 
thYhuScanr: ° f Tne undulation of the hurricane is a mass of water of 
greater or less diameter, according to the force of the tem- 
pest raised above the ordinary level of the ocean by the at- 
mospheric pressure or other cause. This mass is driven be- 
fore the storm in its course nntil it encounters some obstacle, 
as the mouths of rivers, bays, or coasts, when it often pro- 
duces serious inundations or heavy bores. 
currents of the The currents of a hurricane can be brief! v defined as cir- 

hurricane. 

cular currents, where the tempest is of a rotary type. 

There are also in every hurricane two forces, independent 
of that of the wind, which act upon a vessel, the one drawing 
her directly in the line of the path of the storm, the other 
drawing her toward the circumference of that portion of the 
rotary circle where she is placed ; thus, while the drift due 
to the undulation of the hurricane sets toward the AY., the 
current of the hurricane will set toward the "W. on the 
northern portion of the rotary circle: it will set to the E. on 
the southern x>art of this circle, to the S. on the western por- 
tion, and to the X. on the eastern portion of the same cir- 
cle. If the rotary motiou is from E. to W. passing by the 
N., as in the hurricanes of the northern hemisphere, the 
rotary motion would be in the opposite direction in the hur- 
ricanes of the southern hemisphere.* Electricity seems to 



* Inquiry into theXature and Course of Storms. 



9 

take a great part in hurricanes, though very often it may 
escape observation. 

Among the thirty -two hurricanes of the Indian Ocean, of 
which the data is precise, eleven have been accompanied by 
thunder and lightniug, while in twenty-one no electric phe- 
nomena were observed. Thom says* that these phenomena 
are five times more frequent on the north side of the curve 
of translation of hurricanes than on the south side; that is, 
in the position where the monsoons of the W. prevail. He 
adds that it was so common for lightning in the IS", and N. 
W. to precede a gale that the Dutch captains when going 
from the Cape of Good Hope to India had orders to reduce 
sail and take every precaution when they saw lightning. 

In addition to the menacing aspect of the sky which gen- 
erally precedes all storms, that thick circle around the sun or 
moon, clouds heaped up and distended with their gloom}' 
lines of light and their fantastical colors, often of copper 
color, forming a heavy curtain at the horizon, with mena- 
cing points and lines of pale lightning, is known to every 
sailor. These clouds rise little by little, covering soon the 
whole horizon. In approaching the zenith, squalls form be- 
fore the strength of the tempest, the rain falls in torrents, 
and at the same time the hurricane bursts, f 

The barometer and sympiesometer are most valuable in- 
struments in the region of hurricanes, and should be atten- 
tively consulted. In these regions a great fall of the mercury 
below its ordinary level never takes place without being 
followed by a tempest. We have given above its course in 
hurricanes. 

Heavy rains always accompany tempests of a rotary type. 
At a distance of one hundred miles from each side of the 
rotary circle, there is a heavy bank of clouds giving out 
torrents of water without interruption, and this during 
several weeks. 

Hurricanes seldom penetrate into the Gulf of Mexico, 
though three or four have ravaged its coast, and reached as 
far as Vera Cruz ; among others, that of 18th of August, 
1810, and that of 23d of June, 1831. 

NAUTICAL DIRECTIONS TO AVOID HURRICANES. 

EXTRACT FROM THE MEMOIR OF M. KELLER. 

We will recapitulate for each hemisphere the nautical 
directions for attempting to avoid the violence of hurricanes, 

* Horn-Book of Storms. 

t Hurricanes, Tornadoes, Typhoons, and Tempests, &c. 



10 

in order to facilitate their application by navigators threat- 
ened to be enveloped by these storms. 

IN THE NORTHERN HEMISPHERE. 

Hurricanes of West Indies, Cyclones of India, Typhoons of 

the China Sea. 

" If the wind hauls by the compass to the right, or in ac- 
cordance with the movement of the hands of a watch, yon 
are in the dangerous semicircle of the tempest, and, what- 
ever may be the latitude, yon should heave-to on the star- 
board tack, or, if the force of the wind is not too great, 
stand on close-hauled on the starboard tack. 

" If, on the contrary, the wind hauls by the compass to 
the left, or in an opposite direction to the movement of the 
hands of a watch, you are in the manageable semicircle of 
the tempest ; and, if the sea is not too heavy, you should 
run with the wind on the starboard quarter, or, if the sea 
is too heavy, heave-to on the port tack." 

IN THE SOUTHERN HEMISPHERE. 

Hurricanes in the Channel of Mozambique, Island of Bour- 
bon, d'C. 

"If the wind hauls by the compass to the left, or in a di- 
rection opposite to the movement of the hands of a watch, 
you are in the dangerous semicircle of the tempest •; and, 
whatever be the latitude, you should heave-to on the port 
tack, or, if the storm is not too heavy, stand on close-hauled 
on the port tack. 

" On the contrary, if the wind hauls by the compass to 
the right, or in accordance with the movement of the hands 
of a watch, you are in the manageable semicircle of the 
tempest ; and, if the sea is not too heavy, run with the wind 
on the port quarter. If the sea becomes too heavy, heave- 
to on the starboard tack. 

" We will further add that, after having experienced a hur- 
ricane in less than 26° S. or 30° X. latitude, you should not 
for some days steer toward the Pole, to avoid again encoun- 
tering the branch of its path the farthest removed from the 
Equator; for although the velocity of its movement ex- 
ceeds greatly that of a ship, yet the latter may describe the 
chord which joins two points of the curve of the hurricane 
in the same time employed by the meteor to run over the 
arc of this chord. 

" This precaution would be superfluous in the hurricanes 



11 

of the Gulf of Bengal and in the typhoons of the China 
seas, for these seas only extend to 30° N. latitude, and only 
contain a limited and sensibly rectilineal portion of the gen- 
eral path of hurricanes, which spend themselves on the land 
when directed toward the N. W. 

" These practical directions are independent of the lati- 
tude ; they apply to all the routes of typhoons and assure 
escape in the right direction when this is possible." 

EXTRACT FROM A SUBSEQUENT MEMOIR OF M. KELLER, RELATING TO 
MANEUVER IN HURRICANES, CYCLONES, TYPHOONS, AND TEMPESTS. 

" The gyratory movement of hurricanes determines the 
tack. 

"The movement of translation decides the course a ship 
should take. 

"In the northern hemisphere the gyratory movement is 
opposite to the movement of the hands of a watch, and in 
the southern hemisphere it is in the same direction as that 
movement. 

" The gyratory movement being invariable in each hemi- 
sphere, the tack upon which a ship should be placed is 
equally invariable. It is the starboard in the northern 
hemisphere and the port in the southern hemisphere. 

" The movement of translation of the hurricane determines 
for both hemispheres : 

"1. In the dangerous semicircle, the course close-hauled, 
as long as the barometer falls, and with the wind free when 
it rises. 

"2. In the manageable semicircle, the course with the 
wind on the quarter as long as the barometer falls, and with 
the wind free when it rises. 

"The dangerous semicircle being to the right of the path 
of the center in the northern hemisphere and to the left in 
the southern hemisphere, the course of escape — that is to 
say, the route which should be pursued to increase the dis- 
tance from the center of the hurricane — will be known, if it 
is known on which side of the path of the center of the hur- 
ricane the ship is placed j now the side is indicated by the 
variation of the wind by the compass, produced by the 
change of the place of the center of the storm. 

".If in looking in the eye of the actual wind, the wind as 
it hauls blows from the right, the ship is to the right of the 
path of the center. If, on the contrary, the wind as it hauls 
blows from the left of the actual wind, the ship occupies a 
position to the left of the path of the center ; after this, the 
route to be pursued to increase the distance from the center 
depends exclusively on the variatiou of the wind. 



12 

■ ■ This variation should be observed hove-to, in order that 
it be the result of the change of the base of the cyclone, and 
not the change of position of the shi; besides, it she 
correspond to a fell of the barometer, a distinctive ma: 
the actual penetration of the ship into the body of the hur- 
ricane. 

• ■ The indications of the approach of a hurricane beir. . 
heavy swell, a steady fall of the barometer, and an incr - 
ing violence of the wind, is ->on as these are ol> bbty ed, 
a ship should reduce sail and be hove-to on the starb 
tack in the northern hemisphere and the port tack in the 
southern hemisphere, without taking into consideration the 
direction of the waves* in order tpe the aitei : fch 

storm and be in a position to execute, at once, such ulte: 
maneuvers as the variation of the wind, observe! irM 
hove-to, may determine. A resume of these manenve: 
given in the followiri g 

EUVEB I2v HFBBICAZ- THE IHERV HEtfl 

a : TTRKF.. 

2~ >rikem hemisphere, starboard taek. 



-- : - -~- : ■ "^^w 







< J ) 






! 



*• Being hove-to on the starboard tack, barometer falling : 
" 1. If the wind hauls by the compass to the right, or in 
the direction of the movement of the hands of a watch, 
the ship is to the right of the path of the center, in the 
dangerous semicircle, and should run close-hauled on the 
starboard taek. and keep this course until the barometer 
rises, and then run free. 

-. If the wind hauls by the compass to the left, or con- 



13 

trary to the movement of tlie hands of a watch, the ship is 
to the left of the path of the center, in the manageable semi- 
circle of the cyclone, and should run with the wind on the 
starboard quarter, and maintain this compass course during 
the ulterior changes of the wind until the barometer rises j 
from this time shape a course free. 

" 3. If the wind, as noted when hove-to, does not change 
its direction during the progressive fall of the barometer, 
the ship is in the path of the center, and should run with 
the wind aft and keep the same compass course on the star- 
board tack until the barometer rises ; from this moment a 
course free should be maintained to the end of the storm." 



MANEUVER IN HURRICANES IN THE SOUTHERN HEMI- 
SPHERE. 

Southern hemisphere, port tack. 

3. Wind aft. 



1. Close-hauled. 



Free. 



Free 




2. Wind on quar- 
ter. 



Free. 



Free. 



u Being hove-to on the port tack, the barometer falling: 
"1. If the wind hauls by the compass to the left, in a di- 
rection contrary to the movement of the hands of a watch, 
the ship is to the left of the path of the center, in the dan- 
gerous semicircle ; she should run close-hauled on the port 
tack, and preserve this course until the barometer rises, and 
then shape a course with the wind free. 

" 2. If the wind hauls by the compass to the right, in ac- 
cordance with the movement of the hands of a watch, the 
ship is to the right of the path of the center, in the manage- 
able semicircle of the storm, and should run with the wind on 
the port quarter and maintain this compass course during 



14 

the ulterior changes of the wind until the barometer rises 5 
when shape a course free. 

a 3. If the wind, observed when hove-to, does not change 
its direction during the progressive fall of the barometer, 
the ship is in the path of the center, and should ran before 
the wind and keep the same compass course on the port 
tack until the barometer rises ; a course with the wind free 
should be constantly maintained until the end of the storm. 

" These directions relative to maneuvers in hurricanes in 
the two hemispheres differ from those of page 19 of our 
memoir on hurricanes, tornadoes, typhoons, and tempests, 
as the maneuvers advised by Eeid, in his recent work, The 
Progress of the Development of the Law of Storms, page 27, 
differ from those recommended in the two editions of his 
first work, The Law of Storms, which has been extolled by 
Piddington, Thorn, &c. 

" The latter work advised heaving-to on the port tack in 
the manageable semicircle of hurricanes in the northern 
hemisphere and on the starboard tack in the southern hemi- 
sphere, in order to avoid the danger of being taken aback 
in the shifts of wind. But this maneuver having the grave 
disadvantage of pushing the ship toward the center and 
precipitating her into a danger more certain and more for- 
midable, Keid, struck by this disadvantage, advises at pres- 
ent to renounce this mode, and in all cases to take the star- 
board tack in the northern hemisphere and the port tack in 
the southern hemisphere. 

" We are entirely of this opinion, which simplifies the 
maneuvers in reducing them to a question of direction and 
placing the tack out of the case, the more so as, the course 
with the wind on the quarter and the wind aft being sub- 
stituted in the recent directions for hove-to on the opposite 
tacks in the manageable semicircle of hurricanes, ships 
need not fear being taken aback, for the shifts of wind are 
never so great at the commencement of a hurricane as to 
pass from aft forward. • 

" On the other hand, the variation of the wind arising 
from the ship penetrating the base of the hurricane is greater 
in a given time, as the penetration is greater or as the ve- 
locity of the translation of the hurricane is greater. Now, 
this velocity keeping back the wind from the manageable 
semicircle, the wind there is more feeble according to the 
rapidity with which the hurricane advances in its path • 
thence, the greatest variation in the direction of the wind 
which could be feared would be only from a wind compar- 
atively light and by no means formidable ; and if, on the 



15 

contrary, the wind is strong it varies but little, because the 
velocity of the translation is feeble, and then there is no 
danger of being taken aback, although in this case the vio- 
lence of the wind in the manageable semicircle differs but 
little from that in the dangerous semicircle. 

"We will add that the maneuver, wind aft, involves 
a great reduction of sail to manage the ship almost under 
bare poles if the wind is very violent, in order to reduce the 
speed of the ship and the impetus which she communicates 
to the waves, which would be likely to comb over aft if the 
speed were too great. It is always better to run the risk 
of shipping a few seas than to remain stationary, on all 
courses, except that, with the wind aft, it is necessary to 
make sail; otherwise the ship would be at the mercy of the 
waves.' 7 

That navigators may judge of their maneuver by the 
state of the sea, we will show the direction of the predomi- 
nant wave on the different courses prescribed. 

DIRECTION OF THE PREDOMINANT WAVE ON THE DIFFER- 
ENT COURSES. 

In the northern hemisphere, starboard tack. 
The ship being hove-to on the starboard tack : 

On the course pre- ) the predomi ( on the starboard quar- 
scribed free, £ nant wave is ^ ter. 

In the dangerous semicircle : 

On the constant course, ) C 

V the wave is 2 on the starboard beam, 
close-hauled, ) ( 

In the manageable semicircle : 
1st, Wind aft \ /on the port quarter. 

2d. Wind on quarter . . ( ) aft# 

Vtiiewave is< on the starboard quar- 

3d. Windfree I Y + 

i I xer. 

4th. Close-hauled J ( on the starboard beam. 

In the southern hemisphere, port tack. 
The ship being hove-to, port tack : 

On the course pre- ) th OTedomi { ,, , . 

r tne predomi- 1 on ^g p 0r £ q liar ter. 



scribed, free, S Dantwaveis 



In the dangerous semicircle. 
On the constant course, » the nn h i QQ ^ port beam _ 
close-hauled, ' • 



16 

In the manageable semicircle : 

1st. Wind aft... \ / 0I1 t lie starboard qnar- 

2d. Wind on quarter., f J ter. 

\the wave is/ off 

3d. Wind free / \ ' 

I I on the port quarter. 

4th. Close-hauled J (^on the port beam. 

" According to the foregoing, the most unfavorable direc- 
tion of the wave is that of close-hauled in the dangerous 
semicircle, but on this route, the ship being supported by 
the wind, the rolling is not likely to affect the spars ; the 
pitching will be moderate and the helm sm an must watch 
the waves and strive to avoid the shock of the heavy seas. 
This course should not be abandoned, for it is the only one 
by which to avoid future peril, and the skill of the helms- 
man may meet the present danger. The danger here men- 
tioned should never make the mariner neglect the rules laid 
down. He should follow them at all hazards, whatever may 
be the state of the sea, for certainly his situation will become 
more dangerous the longer he delays to execute the maneu- 
ver which alone can secure his safety, by removing from the 
center of the hurricane." 

The following is a resume, for the two hemispheres, of the 
practical directions already given : 

GENERAL REPRESENTATION OF THE MANEUVER IN HURRI- 
CANES, TYPHOONS, AND TEMPESTS. 

As soon as a progressive fall of the barometer and in- 
creasing violence of the wind indicate the approach of a 
hurricane, all the necessary precautions should be taken $ 
heave-to, so as to remain, as nearly as possible, stationary, 
or at least making very little progress, in order to observe 
the wind during the first depression of the barometer and 
to decide from it the course for escape as follows : 
In the northern hemisphere, starboard tack : 
The starboard tack should be taken equally in heaving-to 
at first as for the course of escape. 

If, when hove-to, the barometer falling, 
the wind has not changed its direc- 
tion, run with the wind aft and keep 
this original compass course. 



If the wind hauls to the left, 
run with wind on quarter 
and keep this original com- 
pass course, 

until the barometer rises. 



If the wind hauls to the right, 
run close-hauled and keep 
this course, 



17 

From this moment, and as long as the 
wind is violent, follow the course free 
on the starboard tack. 

In the southern hemisphere, port tack : 

The port tack should be taken equally in heaving to at 
first, as for the course of escape. 

If, when hove-to, the barometer falling, 
the wind has not changed its direction, 
run with the wind aft and keep this 
original compass course. 

If the wind hauls to the left, 



run close-hauled and keep 
this compass course, 



If the wind hauls to the right, 
run with wind on the quar- 
ter and keep this original 
compass course, 

until the barometer rises. 



From this moment, and as long as the wind continues vio- 
lent, follow the course free on the port tack. 

" These practical rules are general and independent of 
all conjecture upon the direction, the velocity, or the radius 
of the storm; they reduce the maneuver to a question of 
courses, the tack being constant and invariable in each 
hemisphere : they should be executed strictly, without any 
thought of the direction of the wave, for being influenced 
by the state of the sea might cause a false maneuver." 

2h 



3> 



2>^ 






^> » » 



sw?> 



3> 



> -» ~:> > 



> >> 

V> - 

» 



-> » 






» > 



> > "> » 

>? > > > . 



>3 









> >3 

-> > 






> ^^> ^3? 5 »--> ^ >^ ^v ^^^ > 



3?> £^ 

TO 



Z*£> 



> 3» »> 






S*^!*?* 



>-~» ^$>7» 



3 r>^l>-^^ A^ 



5> ^>- 






^>>^> 



:> » 



> 3> 






i > V _ 



^31 






i 












>^> ^ l^i- 



5 3 5? i 

> ^ > >: 
► _ > • > ji i> 

> -. 

►> > > 3» > ^ 

> -> 



> -> ^ 



5 >3 



> 3 > 



> > > 's. 

>3) - 



>3$~> >- 

> > ;> 
, -> > > j 

> ■ . > »>■ 

~> > ~ 
> > * 






J- & ! 1 
3,)^ v > 






, ys>3?> - 



3 3 b 



£#*> 






>^f > 



P* S '^ ,y > >V> V> 

^>>> > 3» 



1 



^> j> .3 > > ' 



> ° V - 



> >3> 












> "i3 ■ 






i; y _> ^ 

) > > > _ 

>>0 J> 






-^« ->">"» .v >; > - ' 












> ^>3 












'^^r>^ 



4 r-S ~> 









> > 

> 3 



> 3 



> ^>3> 



■-> > -> ^> > 



^5 > ■> 



- v> 






0>3 3> >TK**3a 

-»i> v 3 :>^ 



: ^>:^^> 



^ ^ "> 3> ^ 



-* --?-^j 






s , > z> 



>3>3 ?-3j-> 
<g „ , ^ ^, 

> 

:j^ ^ 3 



^> ^3>^ 3_^^-_ 



3^> % 
> > > 



3;„^> 



